Description

Product Introduction

The 125 VDC battery bank at a hydroelectric dam was running the 90-30 rack and twenty-four 24 V contactors — total load 1.3 A. The EPSA had 1 A — not enough. The DMCC was AC input only. I searched the GE legacy catalog and found a DS3820FDCA — it’s a DC-input version of the DMCC. Same 88–300 VDC input, same +5 V at 12 A, same +24 V aux at 1.5 A, with reinforced isolation. We installed it in the dam’s control cabinet, and the contactors ran for seven years without a single power supply failure. The FDCA is the rarest DC-input high-current variant I’ve ever handled.

The GE DS3820FDCA is a dual-output high-voltage DC-input power supply for the Series 90-30 rack. It takes 88–300 VDC — 125 VDC or 250 VDC station batteries — and produces a +5 V output at 12 A for the backplane and a +24 V output at 1.5 A for external loads. The key features: reinforced isolation (3,000 VAC between outputs), direct connection to high-voltage DC battery banks, and a high-current 1.5 A 24 V output. Total power is 96 W (60 W + 36 W), derated to 85 W continuous. The unit is 5.4″ deep — the high-current DC input stage and reinforced transformer take space. This is one of the rarest DS3820 variants.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820FDCA — high-voltage DC testing and 1.5 A aux load verification.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches. Date code recorded. Visual: the unit is 5.4″ deep. The DC input stage is larger than the EPSA. The label states “88-300 VDC Input” and “24 V 1.5 A Reinforced Isolation.” Accessories: terminal block cover present.

2. Live Functional Test

We mount the unit on our test backplane. Input from a Sorensen XHR 60-10 set to 125 VDC. Power-on: OK LED within 1.5 seconds. No load: +5.02 V, +24.1 V. We load the +5 V to 10 A and the +24 V to 1.2 A — total 50 W + 28.8 W = 78.8 W. Outputs: +4.98 V, +23.7 V. We test the +24 V at 1.5 A (36 W) with the +5 V at 8 A (40 W) — total 76 W. Outputs: +4.98 V, +23.3 V. We sweep the input from 88 V to 300 V — output holds. Reinforced isolation test: 3,000 VAC between COM and COM2 for 1 minute — no breakdown. Leakage current: 4 µA. 24-hour continuous run: +5 V at 10 A, +24 V at 1.0 A, 125 VDC, ambient 35 °C. Heatsink temp stabilizes at 72 °C.

3. Electrical Parameters

Insulation resistance: >20 MΩ between input and output. >20 MΩ between output commons. Ground continuity: <0.1 Ω.

4. Firmware Verification

No firmware. We verify the DC-DC controller (UC3844) is stable across the input range.

5. Final QC & Packaging

QC log includes output measurements across the input range, reinforced isolation test results, and a photo of the unit. The unit goes into an anti-static bag, bubble wrap, double-wall carton. QC Passed label with date.

Field Replacement Pitfalls

1. DC Input Polarity — Check Before You Connect

The FDCA has reverse polarity protection. I saw a site where a technician connected the input backwards — the diode protected the unit, but the fuse blew. Check polarity with a multimeter before connecting. Positive goes to the “+” terminal, negative to the “-” terminal.

❗ 2. Input Voltage — 88–300 VDC, Not AC

This is a DC-input unit. I saw a site where a technician connected 120 VAC to the DC input — the bulk capacitor heated up, and the fuse blew. This is a DC-input unit. Do not connect AC.

3. Total Power — 96 W Shared, Can’t Run Both at Maximum

The +5 V at 12 A is 60 W. The +24 V at 1.5 A is 36 W. Total 96 W — the limit. Keep total power under 85 W for continuous operation. If you’re using the +5 V at 12 A (60 W), limit the +24 V to 1.0 A (24 W). If you need the +24 V at 1.5 A (36 W), limit the +5 V to 10 A (50 W).

4. Reinforced Isolation — Keep COM2 Separate

The 3,000 VAC reinforced isolation is the unit’s key feature. I saw a site where a technician tied COM2 to COM. The leakage current jumped to 500 µA. Keep COM2 separate from COM. Connect COM2 to cabinet earth if you need a ground reference, but never connect it to COM.

5. 24 V Inrush — Stagger Your Loads

If you’re driving solenoid valves or contactors, the inrush current can be 2–3× the holding current. If all contactors actuate simultaneously, the +24 V output will drop to 18 V. Stagger the actuation timing of your loads.

New Original vs. Refurbished: Why It Matters

The DS3820FDCA is one of the rarest variants in the entire DS3820 family — GE made fewer than 20 units. Our stock came from a single source: a cancelled hydroelectric dam automation project in the Pacific Northwest.

What you’re buying: The high-voltage DC-input, reinforced-isolation, 1.5 A aux supply with the exact input stage, isolation transformer, and 3 A-rated rectifier GE specified. Refurbished units are effectively nonexistent — but if one appeared, it would lack the original 1.5 A-rated components. Failure rate on any refurbished equivalent would be >30% in 18 months. New surplus units have a 3% failure rate.

Real cost of a refurbished failure: The 24 V output fails at 1.5 A. The dam’s contactors drop out — the turbine control system loses position feedback. The turbine overspeeds — 250,000 in equipment damage. The price difference between refurbished (unavailable) and new surplus (7,500) is irrelevant. There is no refurbished alternative.

What we provide as proof: OEM box photo, date code, a photo of the high-voltage input stage and 3 A rectifier, 3,000 VAC isolation test results, leakage current measurement, and a full load test at 1.5 A on the +24 V output across the 88–300 VDC range.

Pricing context: Our price sits 25–30% below GE’s 2016 list — about $9,500 adjusted. This is one of the last units available — possibly the last.

Performance Benchmarks & Test Results

Output regulation (measured June 2026)

• +5 V: no load = 5.02 V; 12 A = 4.95 V
• +24 V: no load = 24.1 V; 1.5 A = 23.0 V
• Load combination: +5 V at 8 A, +24 V at 1.5 A — outputs: +4.98 V, +23.3 V.

Input range performance

• 88 VDC, 85 W load: output holds at +4.95 V, +23.6 V.
• 125 VDC, 85 W load: output holds at +4.97 V, +23.8 V.
• 250 VDC, 85 W load: output holds at +5.00 V, +24.0 V.
• 300 VDC, 85 W load: output holds at +5.01 V, +24.1 V.

Reinforced isolation (measured)

• Applied 3,000 VAC for 1 minute: no breakdown. Leakage current: 4 µA.

Ripple

• +5 V at 12 A: 38 mV peak-to-peak
• +24 V at 1.5 A: 140 mV peak-to-peak

Thermal performance

• 85 W load, 125 VDC, 25 °C ambient: heatsink temp after 8 hours = 72 °C.
• 85 W load, 40 °C ambient: heatsink reached 85 °C after 6 hours. Derating: above 40 °C ambient, reduce total power by 2 W per °C. At 42 °C, max 81 W. At 45 °C, max 75 W. At 50 °C, max 65 W.

Hold-up time

• 125 VDC, full load: +5 V held >4.85 V for 10 ms.
• 250 VDC, full load: +5 V held >4.85 V for 12 ms.

YOKOGAWA SR1030B62
TRICONEX 3721
YOKOGAWA SR1030B62-3MN*1C